The present invention relates to foundry, tooling, processes and methods and more particularly to a core assembly for use in casting operations.
It is known to form castings such as engine cylinder heads by various foundry techniques in which cores of different shapes are placed within a mold to form voids, such as water jacket passages and gas ports for example. In the past, this has required the forming, handling and assembling of numerous cores. A comparatively large number of cores and considerable assembly labor is used in the fabrication of assemblies of this type.
Moreover, conventional core arrangements may require subassembly and pasting or gluing of one or more of the cores together. Such core assemblies are subject to some breakage due to handling, and whenever cores are glued together there are numerous instances in which molten metal flows between the cores and forms fins. When these fins protrude into water jacket passages, they must be removed as they would tend to restrict circulation and interfere with the proper operation of the engine.
Also, in commercial foundries, it is not uncommon for gluing to be performed in such a manner that relatively large amounts of glue remain in hidden or inaccessible areas of the assembled cores. This excess glue acts much as a core would, leaving a void and causing surface imperfections or holes which can necessitate scrapping of the cast piece.
Further disadvantages of conventional core arrangement may include the need for using a large base or positioning core to hold the water jacket cores and port cores in place during core assembly and during pouring.
Another problem associated with conventional cylinder head coring assemblies lies in the need to design the port walls with relatively thick sections in order to allow for proper assembly of the port cores. These thicker than necessary sections have an adverse effect on efficient operation and cooling of the cylinder head.
In certain types of core arrangements, some of the above described problems might be alleviated to a degree by reducing the number of cores in a manner described in U.S. Pat. Nos. 2,820,267 and 2,858,587, issued to Leach on Jan. 21, 1958 and Nov. 4, 1958, respectively. These patents disclose core arrangements for a cylinder head casting in which a number of core-assemblies are combined into a fewer number of cores. The resulting cores are each considerably more complex to form, requiring greater expenditures of time and expense. In addition, the core assemblies disclosed in these patents require the water jacket cores and port cores to be positioned on the green sand in a drag half of a mold in order to maintain their proper spatial relationship. This, in turn, requires the formation of recesses, ridges and projections in the green sand of the mold of sufficient precision to provide the required alignment. Further, the water jacket and port cores cannot be assembled accurately in the absence of the drag half of the mold. This type of assembly is useful only when the core subassemblies can be combined and is commercially inapplicable to many types of core assemblies in which intermediate cores can only be located within the core assembly before certain other outer cores are positioned in place.
The search has thus continued for a commercially acceptable method of providing a core arrangement which eliminates gluing of cores and its resulting disadvantages and which provides for fewer core components.
It is, therefore, an object of the present invention to provide novel methods and tooling for minimizing or eliminating problems of the sort dicussed above.
It is another object of the invention to provide a novel core assembly and novel methods for fabrication thereof.
It is another object of the present invention to minimize the formation of fins and surface imperfections in casting operations.
It is another object of the invention to eliminate the need for a positioning core in casting operations.
It is a further object of the invention to improve the cooling characteristics of cast cylinder heads.